This invention relates to machines for spinning textile fibers by the open end method, whereby fibers are fed into a cavity of a spinning rotor, where they are spun into thread. A typical open end spinning unit is described in U.S. Pat. No. 3,807,157, issued Apr. 30, 1974 to Fritz Stahlecker. More particularly this invention relates to an open end spinning machine in which a plurality of spinning units, their associated winding units and auxiliary components are mounted upon and structurally supported by a rigid backbone extending longitudinally between ends of the machine, as described in my copending patent application Ser. No. 585,968, filed on June 11, 1975. Such machines employ a vacuum system connected to the spinning chamber and sometimes to a cleaning chamber in each spinning unit. In the usual construction one duct extending the length of the machine is connected between a vacuum producing source and each of the spinning chambers, while another duct extending the length of the machine is connected between another vacuum producing source and each of the cleaning chambers. Different vacuum sources are employed because of the difference in vacuum pressures employed.